[Mac][Material Design] Use white tab spinner for dark themes.

chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "chrome/browser/ui/cocoa/tabs/tab_strip_controller.h"
 
 #import <QuartzCore/QuartzCore.h>
 
 #include <cmath>
 #include <limits>
@@ skipping 1546 matching lines @@
 
   TabLoadingState oldState = [tabController loadingState];
   TabLoadingState newState = kTabDone;
   NSImage* throbberImage = nil;
   if (contents->IsCrashed()) {
     newState = kTabCrashed;
     newHasIcon = true;
   } else if (contents->IsWaitingForResponse()) {
     newState = kTabWaiting;
     if (ui::MaterialDesignController::IsModeMaterial() &&
-        [[[tabController view] window] inIncognitoMode]) {
+        [[[tabController view] window] hasDarkTheme]) {
       throbberImage = throbberWaitingIncognitoImage;
     } else {
       throbberImage = throbberWaitingImage;
     }
   } else if (contents->IsLoadingToDifferentDocument()) {
     newState = kTabLoading;
     if (ui::MaterialDesignController::IsModeMaterial() &&
-        [[[tabController view] window] inIncognitoMode]) {
+        [[[tabController view] window] hasDarkTheme]) {
       throbberImage = throbberLoadingIncognitoImage;
     } else {
       throbberImage = throbberLoadingImage;
     }
   }
 
   if (oldState != newState)
     [tabController setLoadingState:newState];
 
   // While loading, this function is called repeatedly with the same state.
@@ skipping 740 matching lines @@
 
 - (void)themeDidChangeNotification:(NSNotification*)notification {
   [newTabButton_ setImages];
 }
 
 - (void)setVisualEffectsDisabledForFullscreen:(BOOL)fullscreen {
   [tabStripView_ setVisualEffectsDisabledForFullscreen:fullscreen];
 }
 
 @end